This invention relates to the remote surveillance of equipment such as repeaters located along a digital transmission link. More specifically, it concerns remote surveillance utilizing signaling incorporated in the traffic on the basis of time division multiplexing with the data.
Remote surveillance systems of this type are already known in which signalling uses an identifier specific to each item of equipment followed by a reply block. These identifiers must be distinguishable from the data, this normally being obtained by making them of sufficient length for it to be highly improbable that a data burst would be identical. This method has the drawback that it does not totally eliminate a risk of confusion with data and requires long identifiers for remote surveillance which occupy the link disportionately.